US4383271A - Thermal imager - Google Patents

Thermal imager Download PDF

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Publication number
US4383271A
US4383271A US06/263,098 US26309881A US4383271A US 4383271 A US4383271 A US 4383271A US 26309881 A US26309881 A US 26309881A US 4383271 A US4383271 A US 4383271A
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US
United States
Prior art keywords
detector
scanner
waveform
scene
radiation
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US06/263,098
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English (en)
Inventor
Charles A. Berry
Peter J. Berry
Ian H. Howie
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales Optronics Ltd
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Thales Optronics Ltd
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Filing date
Publication date
Application filed by Thales Optronics Ltd filed Critical Thales Optronics Ltd
Assigned to BARR & STROUD LIMITED, A BRITISH COMPANY reassignment BARR & STROUD LIMITED, A BRITISH COMPANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: BERRY CHARLES A., BERRY PETER J., HOWIE IAN H.
Application granted granted Critical
Publication of US4383271A publication Critical patent/US4383271A/en
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/30—Transforming light or analogous information into electric information
    • H04N5/33—Transforming infrared radiation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N3/00—Scanning details of television systems; Combination thereof with generation of supply voltages
    • H04N3/02—Scanning details of television systems; Combination thereof with generation of supply voltages by optical-mechanical means only
    • H04N3/08—Scanning details of television systems; Combination thereof with generation of supply voltages by optical-mechanical means only having a moving reflector
    • H04N3/09—Scanning details of television systems; Combination thereof with generation of supply voltages by optical-mechanical means only having a moving reflector for electromagnetic radiation in the invisible region, e.g. infrared
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/20—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from infrared radiation only
    • H04N23/23—Cameras or camera modules comprising electronic image sensors; Control thereof for generating image signals from infrared radiation only from thermal infrared radiation

Definitions

  • This invention relates to thermal imagers.
  • the scene from which the thermal infrared radiation emanates is scanned continuously by an optical scanner across a detector the output signal waveform of which is fed through signal processing circuitry to a video output device.
  • the scanner scans two-dimensionally but the detector output signal is substantially continuous being composed of successive waveform portions arising from the time interval that the detector is effectively scanned across the interior of the imager housing and the time interval that the detector is effectively scanned across the scene.
  • the detector output signal therefore has a periodical structure the period T being conveniently measured from the end of the waveform portion due to a first scan across the scene to the end of the waveform portion due to the next scan across the scene.
  • the waveform portions due to the scene-derived information are also of constant duration T 1 , the scan efficiency of the imager being the ratio T 1 to T.
  • a thermal imager wherein the detector output waveform has a period T, the scene-derived waveform has a duration T 1 , where T 1 ⁇ 50%T, the sync signal is located prior to and closely adjacent the scene-derived waveform, the duration from the sync signal to the end of the scene-derived waveform is T 2 and the monostable has a set time T 3 such that T 2 ⁇ T 3 ⁇ 50%T.
  • the monostable is set for a duration greater than T 1 but less than 50%T so that even if the monostable is prematurely activated it will have reverted to its off condition prior to the sync signal during the next period T of the detector output signal so that correct synchronisation will then occur, resulting in only a single line of unintelligible video.
  • the scan efficiency is less than 50% the waveform portion due to the detector being scanned across the interior of the imager housing has a duration greater than T 1 and during this period the detector output requires to be devoid of a waveform which could be recognised erroneously by the recognition circuit. This however is easily achieved since the interior of the imager housing is of a predetermined nature.
  • the sync signal may conveniently be provided by a mirror within the imager housing and reflecting infrared radiation from the detector mount (which is cooled substantially below ambient temperature) back onto the detector.
  • FIG. 1 shows a thermal imager in block form
  • FIG. 2 illustrates the waveforms therefrom.
  • FIG. 1 The drawing illustrates in FIG. 1 a thermal imager 10 comprising a housing 11 having a window 12 through which thermal infrared radiation from the scene is incident on a scanner 13.
  • the scanner 13 focusses this radiation on a detector 14 resulting in an image of the detector 14 effectively being scanned along a line locus 15 within the housing 11 on which lies a mirror 16 for providing a sync signal by the narcissus effect from the mount 14A of detector 14 since the latter is cooled substantially below ambient.
  • Any alternative known form of arrangement for providing such a sync signal would suffice however.
  • the detector output is fed along signal path 18 to a sync signal recognition circuit 20 which extracts the sync signal and uses the extracted sync signal to activate a monostable forming part of a clock arrangement 22.
  • the detector output signal is also fed along path 23 to the signal processing circuitry 24 and hence to the video output device 25 both of which are clocked by clock arrangement 22 for synchronisation.
  • the form of the detector output signal 30 is illustrated in FIG. 2, being formed of successive waveform portions 30A, 30B, 30C, 30D and 30E.
  • Portion 30A is representative of a first scan line containing scene-derived information;
  • 30B represents the waveform due to the interior of the housing 11;
  • 30C is the sync signal;
  • 30D is a second scan line having a similar but not-necessarily identical waveform to portion 30A;
  • 30E is the same as 30B.
  • the function of portions 30A and 30B represents the beginning of a period T terminating at the junction of portions 30D and 30E when the next period commences.
  • Portion 30D is of duration T 1 such that T 1 ⁇ 50%T and the sync signal is located closely adjacent and prior to the portion 30D.
  • the duration T 2 from the junction of portions 30B and 30C to the end of the period T is also less than 50%T.
  • the sync signal recognition circuit 20, which conveniently may comprise a differentiator and threshold device recognises the presence of the sync signal portion 30C and sets the monostable of the clock arrangement 22 for a time interval T 3 such that T 2 ⁇ T 3 ⁇ 50%T as shown in FIG. 2, the leading edge 28A of the monostable set portion being aligned in time with the sync signal and the trailing edge 28B of the monostable set portion being after the termination of T 1 and T 2 and T.
  • waveform portions 30B and 30E are devoid of anything resembling the sync signal portion 30C whereas portions 30A and 30D, being scene-derived information contain peaks such as 31 which in the absence of the present invention could lead to erroneous operation of the sync-signal recognition circuit 20.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Transforming Light Signals Into Electric Signals (AREA)
  • Radiation Pyrometers (AREA)
  • Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
  • Heat Sensitive Colour Forming Recording (AREA)
US06/263,098 1980-05-22 1981-05-12 Thermal imager Expired - Lifetime US4383271A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8017012 1980-05-22
GB8017012 1980-05-22

Publications (1)

Publication Number Publication Date
US4383271A true US4383271A (en) 1983-05-10

Family

ID=10513615

Family Applications (1)

Application Number Title Priority Date Filing Date
US06/263,098 Expired - Lifetime US4383271A (en) 1980-05-22 1981-05-12 Thermal imager

Country Status (11)

Country Link
US (1) US4383271A (fr)
BE (1) BE888898A (fr)
CH (1) CH655216A5 (fr)
DE (1) DE3119644A1 (fr)
FR (1) FR2483152A1 (fr)
GB (1) GB2076612B (fr)
IN (1) IN154358B (fr)
IT (1) IT1145552B (fr)
NL (1) NL8102455A (fr)
NO (1) NO811735L (fr)
SE (1) SE449034B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6631287B2 (en) 2001-04-03 2003-10-07 Welch Allyn, Inc. Infrared thermometer
US9307912B2 (en) 2012-08-08 2016-04-12 Welch Allyn, Inc. Temperature measurement system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2200813B (en) * 1987-02-03 1991-06-05 Gec Avionics Thermal imager

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1273707A (en) * 1970-11-23 1972-05-10 Mullard Ltd Improvements relating to infra-red thermal imaging systems
US3751586A (en) * 1969-10-29 1973-08-07 Bofors Ab Circuit system for compensating the influence of the back-ground radiation on the picture display in an infra-red camera
US3812483A (en) * 1972-05-26 1974-05-21 Us Army Point source discriminator thermal alarm
US3944730A (en) * 1973-03-06 1976-03-16 Aga Aktiebolag Device for the elimination of the effect of background radiation on the image representation in an ir-camera
GB1444518A (en) * 1974-03-27 1976-08-04 Hughes Aircraft Co Synchronous thermal imaging system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3798366A (en) * 1972-03-06 1974-03-19 R Winkler Infrared imaging system

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3751586A (en) * 1969-10-29 1973-08-07 Bofors Ab Circuit system for compensating the influence of the back-ground radiation on the picture display in an infra-red camera
GB1273707A (en) * 1970-11-23 1972-05-10 Mullard Ltd Improvements relating to infra-red thermal imaging systems
US3812483A (en) * 1972-05-26 1974-05-21 Us Army Point source discriminator thermal alarm
US3944730A (en) * 1973-03-06 1976-03-16 Aga Aktiebolag Device for the elimination of the effect of background radiation on the image representation in an ir-camera
GB1444518A (en) * 1974-03-27 1976-08-04 Hughes Aircraft Co Synchronous thermal imaging system

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6631287B2 (en) 2001-04-03 2003-10-07 Welch Allyn, Inc. Infrared thermometer
US9307912B2 (en) 2012-08-08 2016-04-12 Welch Allyn, Inc. Temperature measurement system
US9474450B2 (en) 2012-08-08 2016-10-25 Welch Allyn, Inc. Temperature measurement system
US9901258B2 (en) 2012-08-08 2018-02-27 Welch Allyn, Inc. Temperature measurement system

Also Published As

Publication number Publication date
SE449034B (sv) 1987-03-30
IN154358B (fr) 1984-10-20
NL8102455A (nl) 1981-12-16
FR2483152A1 (fr) 1981-11-27
SE8103261L (sv) 1981-11-23
DE3119644A1 (de) 1982-04-29
FR2483152B3 (fr) 1983-03-04
NO811735L (no) 1981-11-23
BE888898A (fr) 1981-09-16
CH655216A5 (de) 1986-03-27
GB2076612A (en) 1981-12-02
GB2076612B (en) 1984-01-25
IT1145552B (it) 1986-11-05
IT8167675A0 (it) 1981-05-20

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